Process of reclaiming devulcanized rubber.



, UNITED sraras PATENT OFFICE..-

I ERVIN EMIL ALBERT GEORG MEYER, OF NEW BRUNSWICK, NEW JERSEY.

PROCESS RECLAIMILTG DEVULGANIZED RUBBER.

No Drawing.

following is a specification.

.The object of my inventionis a process of converting devulcanized rubber by depolymerization into a rubber which possesses practically the properties'of natural rubber. By the term devulcanized rubber as here used, I mean rubber which has Once been vulcanized and afterward subjected to a treatment to remove substantially all the added ingredients.

. My invention consists in treating devulcanized rubber with a neutral soap prefen ably made of the resin which accompanies natural rubber. In this manner the dev.ul-

ca'nized rubber is depolymerized and thus assumes again the properties characteristic of natural rubber. The soap is produced by saponifying that resin which accompanies natural rubber.

Rubber in the devulcanized state cannot be used for manufacturing purposes with the same success as natural rubber, but rubber in the depolymerized state, as obtained by practicing this invention, assumes again the properties characteristic of natural rubber and can then be used in the same manner, with practically the same success as the natural product. i

In the manufacture of rubber articles,

mineral matter of various kinds are added,

while the rubber itself is also partially re placed by substances, generally consisting of some form of solidified, oils such as blown oils. These additions in general can be easily removed in the process of recovery of waste the rubbersubstance, and partly remains as such in the manufactured rubber, and it is believed that the hydrocarbons contained in Specification of Letters Patent.

Application filed Mayfl, 1907. Serial No. 371,944.

Patented Oct. 12, 1909.

the original rubber substance undergo the so-called process of polymerization by the action of sulfur and heat. Acids' and alkalies and organic solvents have been used for the removal of the mineral matter and solidifie'd oils, and for dissolving out the rubber substance, and it is obvious that those chemicals which have the least injurious influence on theoriginal rubber substance would prove the best materials for the recovery of waste rubber. j

The steps and chemicals used in my process differ from all methods and all processes known in the priorart, in that they apparently depolymerize the hydrocarbons o the rubber substance, without any other change or injurious secondary action, and bring them back nearest to their'original formof molecular constitution in which they are contained in the natural rubber, for the product obtained in my process can be practically used like natural rubber for all purposes.

In order to carry out my process practically I proceed as follows: I employ devulcanized rubber obtained according to any of the processes described in the art, but I prefor that devulcanized article, the production of which I" describe and claim in my application, Serial No. 371,946, and which is made as follows: Rubber waste is cut up into small pieces and mechanically separated from textile fibers and metallic particles. If the textile fiber is so intimately mixed with the rubber that it cannot be separated mechanically, the textile fiber must be removed by a carbonizing process with acids.

\Vhatever is done in this preliminary treatment, the rubber waste must be practically free from moisture before the subsequent addition of the solvents. The dry and coinminuted rubber is then treated with a liquid in a strongly built iron vessel provided with a stirring mechanism and condenser, so that the treatment of the material may be carried on at high temperature and pressure. This vessel is also connected with a pump which supplies the necessary liquid from two separate tanks. For each kilo of waste about six Waste to be treated. The composition of the liquidtalso depends upon the grade of waste. In practice l have found the following proportions to act satisfactorily:

I .2 parts ofrubber solvent to 8 partsof acetone 3 parts of rubbersolvent to 7 parts of acetone 4 4 parts of rubber solvent to 6 parts ofacetone As a rubber solvent I can use phenol,

chloroform, naphtha, gasolene, nitro-benzene, mixtures thereof, or other organic solvents for rubber. ethyl alcohol. The treatment lasts usually from two to fivehours according to the material, and the temperature to' beemployed for the treatment must also be variedaccordingly. If such rubber substitutes as factis are present, the following treatment is additionally recommended. An alcohollc solution of caustic'soclapontaining about two to five per cent. of the alkali is added to the rubberwaste" after the solvents employed in the prior treatment have been removed. Of

this solution enough is employed to perfectly cover the rubber waste. The whole mass is then heated for abouttwo to five hours at the boiling point of the. alcohol and stirred at the same time. The time of treatment varies with the quality. of rubber waste.

' 'lhdproduct thus obtained, will'bea good quality of devulcanized rubber. Instead of an alcoholie'solution of sodium hydroxid, I. can-also use an alcoholic solutlon of potassium hydroxid, bariumhydroxid, etc. The

de'vulcanized rubber is then treated with a neutral soap preferably madefrom resin which accompanies naturalrubber', and is. prepared as follows: One hundred kilos of' rubber resin are heated with two hundred kilos of water, v to which twenty kilos of sodium hydroxid 'are added; the mass is boiled, and to the boiling liquid five kilos of sodium carbonate are added. For each one hundred kilos of rubber to be treated,

ten kilos of resinous soap are taken. Then the rubber is heatedwith the soap to a tem perature of about 140 to 210 degrees 6.,- at a pressure of from. three to fifteen atmos pheres, according, tothe quality of material to be treated. The treatmentmay'lastfrom two to five hours. For some rubber waste it is advantageous to employ a larger quantity of resinous soap, and good results were obtained by increasing the amount of resinous soap to thirty per cent. of the quantity of the waste rubber used in the process. It has also been found that the resins extracted from some qualitiesof natural rubber do not easily yield soaps which can be successfully employed in the'process ofdepolymerization, The production of the resinous soap might then advantageously be modified as follows: To one hundred parts of resin ten parts of cocoanut oil are added and this-mass is heated with a solution contain- Instead of acetone I can use.

Letters Patent is:

ing tenparts of caustic soda, dissolved in fifty parts of water, and two parts of sodlum carbonate, also dissolved in fifty parts of water. To this mixture two hundred parts of water aregradually added until a com plete solution is obtained. The resin soap might also be made by melting together the kalies, such as carbolicacid.

depolymerizing d-evulcanized rubber, I do not wishto be understood as excluding from my claim equivalents for the ingredients, the" apparatus, or the operationsjemployed in the process- It is probable thatsubstitutes may be employed without departing from "the scope ofthe process intended to'be secured hereby.

Although I have above described aniexample of carrying out. my. new'processfof pounds, capable of forming salts withallVhen I use the term' devulcanized rubber I mean specifically rubb erwasteewhich has been subjected to a treatment for the removal of sulfur, and filling ingredients-f 'Of course, nonebf such treatments wholly removes the materials added to the rubber.

Having now described my. invention and in what manner the same is tobe performed,

what I claim as new and desire to secure by L'The process of depolymerizing devu1- canized rubber consisting in treating devulca'nized rubber with a neutral resmous soap at temperaturesover 120 C. 2. The process of depolymerizing devul canized rubber, consistingin treatingdevulv canized rubber with a neutralresinous soap associated with an oil capable of saponification at a temperature in excess of 120 C.

i .3. The process of depolymerizing devul canizedrubber consisting in. treating devulcanized rubber with a neutral resinous soa associated with anoil capable of saponi cation under pressure 1n excess of atmospheric pressure and'at a temperature in ex-' cess of=120 C.

4. The process of .depolymerizing rubber waste, which consists in first devulcanizing the same by treating it 'with a mixture of two solvents, the one of which is a rubber solvent, while the other -is'not, and finally treating it with a neutral resinous soap at a temperature in excess of 120.? C. and under pressure in excess of atmospheric pressure. 5. The'process of depolymerizing rubber waste, which consists in first devulcanizing testes the same by treating it with a mixture of two solvents, the one of which is a rubber solvent, while the other is not, and finally treating it at high temperature and pressure with a neutral resinous soap made from the resin accompanying natural rubber.

6. The process of depolymerizing rubber waste, which consists in first devulcanizing the same by treating it with a mixture of rubber solvent and acetone, and finally treating it with a neutral resinous soap, at a temperature in excess of 120 C.

7. The processof depolymerizing rubber waste, which consists in first devulcanizing the same by treating. it with a mixture of rubber solvent and acetone, and finally treating it with a neutral resinous soap made from the resin of natural rubber, at high temperature and pressure. I

8. The process of depolymerizing rubber Waste, which consists in first (levulcanizing the same by treating it with-a mixture 'of rubber solvent and acetone, and finally treating it at high temperature and pressure with .a neutral resinous soap made from the resin accompanying natural rubber associated with an oil capable of saponification.

9. The process of depolyinerizing rubber waste, which consists in first devulcanizing the same, by treating it with a mixture of two solvents, the one of which is a rubber solvent while the other is not, and subjecting it to the action of an alcoholic solution resinous soap made from the resin of natural rubber.

10. The process of depoiymerizingrubber waste, which consists in first devulcanizing the same by treating it with a mixture of two solvents, the oneof which is a rubber solvent while the other is not, then subject ing it-to the action of an alcoholic solution of a hydroxid possessing a saponifying action and finally treating it with a neutral resinous soap made from the resin of natural rubber associated with an oil capable of saponification.

11. The process of depolymerizing rubber waste, which consists in first clevulcanizing the same by treating it with a mixture of two solvents, the one of which is a rubber solvent while the other is not, and subjecting it to the action of an alcoholic solution of a hydroxid possessing a saponifying action, and finally treating it, at high temperature and pressure, with a neutral'resinous soap made from the resin of natural rubber associated with an oil capable of saponification.

In witness whereof, have si name in the presence of two witness ERWIN EMIL ALBERT GECRG MEYER. VVitnesses:

H. RICHARD Worse, Y. FRANK Gunnery, 

